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Had a great time demonstrating various types of kite flying at the 24th Annual Kite Day in the Park, in Easton, PA. Great group of people run this event for families and children new to kiting. Had fun flying stunt kites at the beginning of the event, glider kites throughout the day and even my HQ Lutz Treczoks Cody War Kite when the wind was at its peak. Spent most of the day flying the Bird of Prey 48 and 62 glider kites.

According to Weather Underground, the wind ranged from 5.8 to 12.7 mph during the event, with an average wind speed of 10.2 mph. The wind direction was out of the south southwest. The weather was perfect to test out the performance envelope of the larger and higher sail density BOPs. Used 50 pound spectra line and both BOPs flew extremely well. What was a pleasant surprise was the light line tension and responsiveness to minor changes in the line tension under the wide range of wind speeds. Flew most of the time holding the flying line between just two fingers. Even under the higher wind speeds for this type of design, the BOPs maintained their sail shape. As a point of reference, I flew for a very short period of time the heavier framed version of the Rapere 48 canard glider kite when the wind was at a low point. The Rapere 48 pulls like a tank on the climb, which is great for gaining altitude in light wind conditions. What we observed was the BOPs were able to dump the excessive lift in the observed range of wind conditions, which in turn reduces the tension on the flying line.

The BOP 62 is very majestic and smooth in the air, and a real joy to fly. Time just passes by flying this kite and you become very calm and relaxed. Now on to the BOP 48, which has multiple personalities depending on how you handle the flying line. With a light and smooth handling of the flying line, the BOP 48 fly’s exactly like the BOP 62. The fun begins when you get aggressive with the flying line. Quick changes in line tension and the BOP 48 is off climbing, diving, spinning and running down wind. Right when the nose is pointed slightly off of direct downwind while gliding, you add a little line tension and the kite snaps around and climbs right back up to over your head. Was able to do this snap turn many times with the kite just inches off of the ground. The reason the BOP 62 is more stable is due to its size and our arms are not long enough to give the needed input. Very pleased that the CST hollow carbon tube frames held up to my very heavy handed flying. The BOP 48 fly’s just its little brother (BOP 24), but in higher wind conditions. Attending kite flyers thought the BOP 48 flew like a large fighter kite, except the spins are horizontal to the ground like dual line old school axles. The shape of the kite and direction of flight had many people asking what type of kite it was and why was it flying backwards.

Just want to thank two very nice kite flyers, Doug and Art, who spent quite a bit of time with me and the BOPs. Also, Doug and his very nice wife were very instrumental in helping me assemble my Cody War Kite. At various times during the day, I could not resist putting the BOP flying line in their hands. Why should I have all of the fun. They both were asking great questions and what better way to answer some of their questions was by their own experience in flying the kites. Their calm expressions that turned into broad smiles made all of my development efforts worthwhile. Later in the day, most of the fields were occupied by parents and kids flying newly made kites. Doug and I looked at each other and just smiled. We both wanted to fly the BOP 48 again and were trying to figure out where. We found an area near the food pavilion and event tents, where the currently leafless trees would screen the wind a little to reduce the wind speeds. Yes, we were looking for and flying next to trees and the BOPs love the air conditions. Art joined us in this area and we had a great time. We spend many hours throughout the day flying these kites.

In closing, the BOP 48 and 62 are very response glider kites for winds ranging from 0 to 5 mph and can park in the sky in winds up to 10 mph. The unique shape provides several benefits that make this kite a real joy to fly. I hope to get them back out in 0 to 5 mph smooth winds in the near future.

After all of this fun and at the request of others, I will revisit and simplify the PC31 sail pattern and build a few for other glider kite enthusiasts. Based on our extensive flying of the BOP 48, this will be the size that I will initially build for others. We just love its responsiveness to different flying styles.

The attached file provides my proposed new layout for the panels on the PC-31 version of the Bird of Prey 48. The colors are my old favorite red, white and blue, with a black nose. Time to add some curves to this kite. Please let me know what you think of the layout.

If you have been following my development of the Bird of Prey (BOP) glider kite, you will know that I am pleased with the design for the ultra-light and low wind versions of the kite. In the spirit of sharing the joy of this design with others, I will post links in the near future with the plans for the BOP 24 made with Cuben fabric, and the BOP 48 made with PC31. Please note that you will need the patients and finger dexterity of a Swiss watch maker to the build a BOP 24. The following provides my conditions when I offer the plans:

• When you download the plans for either design, you provide a financial contribution to this great kite forum. When you complete your BOP, you post a picture or video on this great kite forum.

• There will be a note on the plans that indicates the designs are not being offered for someone to build and sell the kite to others for a profit.

• If you are not comfortable in building a BOP yourself, just send me a note and I will build one for you. For the BOP 48, the color selection is up to you, with my guidance. The reasonable fee I request for the construction of either BOP allows me to replace my building materials, so that I can continue my research efforts that brought you the Hawks, Raperes, and now the Birds of Prey.

As indicated in my previous posts, I am finalizing the plans for a new panel layout for the BOP 48, which I hope to have done in the near future. I should be able to make the plans available before June of this year. I will build a new BOP 48 using the new panel layout and post my progress and pictures on this great forum.

There are other sizes of the BOP, which are very rewarding to fly. I may in the future offer the plans for the ultra-light BOP 36 and BOP 48 made with Cuben fabric, and the BOP 62 made with PC31.

Four more Bird of Prey 24s out the door to fellow glider kite enthusiasts. Will start finalizing the plans for the Bird of Prey 24, then work on the new layout for the Bird of Prey 48. I am having a blast with the spline function in AutoCAD to generate nice curves for the panel seams.

Thank you for your kind words. I do enjoy developing these unique and well flying glider kites.

The attached file provides my latest pattern layout for the Bird of Prey 48, using my default red, white and blue colors, with a black nose.

Had fun using the Spline line drawing feature in AutoCAD, not to be confused with spline feature when editing a Polyline. The Spline feature lets the line fitting equation draw the line through the line anchor points, which is not the case with the spline feature when editing a Polyline. I also tried the good old Fit Curve feature when editing a Polyline, put it did not give me the same curve. When using the Spline line drawing feature, I started at the trailing edge and worked to the leading edge. Just to see what happens, I drew a second Spline line that started at the leading edge and ended at the trailing edge, using the same line anchor points. The line had a different curve to it, which I did not like or use.

I think this is the pattern version I am going to go with for my new build and the plans. If you have any other suggests, let me know.

This color layout has the black, brown and tan colors reversed. Please note on both versions with the bird type colors, the addition of yellow as the nose reinforcement. One would add a layer of yellow PC31 over the dacron reinforcement material, which would be white.

Back on March 29, 2014 in Post 171, I indicated I reframed the Birds of Prey (BOP) 36 and 48 made with Cuben fabric using the CST carbon tubes. Until yesterday, I haven't had the right weather conditions to really give them a thorough evaluation. Yesterday, I finally had the right conditions early in the morning. First up was the BOP 24 to check the weather conditions, then the BOP 36 and the BOP 48. The BOP 48 is a good glider at the very light weight of 11.3 grams, with a sail loading of 0.0217 grams/square inch of sail area. The climb is reasonable and it fly’s very smooth like its big brother the BOP 62, but I am still tinkering with this kite. You will see why in a moment. As a point of reference, the BOP 24 has a sail loading of 0.0208 grams/square inch of sail area.

Now we come to the BOP 36. This glider is very light at 5.7 grams and had the lightest sail loading of all of the BOPs, at 0.0195 grams/square inch of sail area. Even with the new 0.039 inch diameter CST carbon tube frame, the frame is just too small in diameter to be stiff enough for this kite when under load for a good climb. Great glide, but just does not want to climb above 15 feet in no wind conditions.

The ideal carbon tube frame diameter would be around 0.05 inches, but no one makes one in that size. I had a spare length of the CST 0.059 inch carbon tube in my work shop. This carbon tube (0.508 grams/inch) is lighter than a carbon rod with a 0.05 inch diameter (0.0552 grams/inch), which would be the diameter I would try next. My concern going to this larger diameter and stiffer frame is that the BOP 36 would be too ridged and not adjust to sail loads like the BOP 24 and the BOP 48 made with PC31. I replaced the frame and the center joiner, which increased the overall weight of the kite by 1.45 grams for a total weight of 7.15 grams. This is an increase of 25% in weight, with a new sail loading is 0.0245 grams/square inch of sail area. As with the lighter frame, this glider kite did not required additional nose weight, which is a good thing. The assemble BOP 36 is very stiff, but the trailing edge of the wing tips still can move under load. At that time, I was concerned that I am taking the design in the wrong direction, using a much stiffer frame that caused a 25% increase in sail loading.

I flew the BOP 36 yesterday evening in no wind conditions and I am shocked about how well this kite fly’s! The climb is outstanding and the glides are long and flat. This kite went from being a floater to a real performer. It’s very responsive to any changes in line tension, and I can spin this kite at altitude above my head in no wind conditions. Based on this success, I may try a stiffer frame in the BOP 48 made with the Cuben fabric.

In closing, we strive to get our gliders as light as possible, but sometimes sacrifice the minimum frame stiffness needed for the kite to perform outside of a gentle flat glide. With our glider kite designs, there also is a minimum sail loading that allows the kite to perform. If we go below that minimum sail loading, we can sacrifice performance. Since we try to design our kites around available materials, it’s an art to marry the right frame to the design, in order to obtain the maximum performance.

The attached picture shows the PC31 panels cut out for the Bird of Prey 48, using the new pattern layout. You can't see the white between the red and the blue. The nose is charcoal in color, which is the color I used on the prior version. The blue strips near the wing tips are the wing spar sleeves, also made from PC31. Time to tape together the panels.

Due to the file size limitation of 100K, if you click on the picture, the edges will look jagged. When I finish this kite, I will post a link to the pictures not in the reduced file size.

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